This invention relates to drum head tensioning mechanisms of or for a musical drum.
A musical drum consists of a cylindrical drum shell over the open ends of which respective drum heads are tensioned. Each drum head consists of a circular "skin" having a diameter slightly greater than the diameter of the drumshell, a flesh hoop being secured to the periphery of the skin. The skin rests against an annular bearing edge of the drum shell with the flesh hoop lying alongside the outer surface of the drum shell.
In order to tension the skin, pressure is applied to the flesh hoop in a direction away from the bearing edge. Pressure may be applied to the drum shell in a variety of ways. Many of the ways involve the provision of fittings such as brackets secured to the drum shell and against which a skin tensioning device may bear or be secured. A disadvantage of this type of arrangement is that the inner cylindrical surface of the drum shell is disturbed, for example, by securing bolts for the brackets, thus removing the drum shell's clean inner surface and so causing a deterioration in the sound quality produced.
A further problem associated with this type of construction is that the mechanical strength of the drum shell is weakened and the shell tends to become damaged under excess tension or even the tensions normally applied to military and pipe band drums, which are of the order of 80 to 100 psi.
In other types of drums, the drum shell is located within a cage, the skin tensioning devices being secured to the cage rather than the drum shell. This type of construction enables the drum shell's inner surface to remain clean and at the same time enables at least some of the mechanical stress resulting from. tensioning of the drum heads to be carried by the cage rather than the drum shell per se.
In a known construction of this type, a counterhoop is placed over each drum head and a plurality of peripherally spaced bolts connected between the top and bottom counterhoops. A particularly advantageous form of this construction is described in United Kingdom patent application No. 2,201,026,in which a plurality of bolt adjusting assemblies for the top and bottom counterhoops are provided. The bolt assemblies for the top counterhoop are angularly offset with respect to the bolt assemblies for the bottom counterhoop.
While a musical drum is being played, the tension of the skin may vary and it is therefore necessary to be able to adjust the tensioning of the skin. It is of course particularly desirable that this adjustment should be capable of being carried out as quickly and conveniently as practicable, with the least possible interruption to the performance.
The known drums of counterhoop construction, as described above, have the disadvantage that access is required to both the top and bottom faces of the drum in order to be able to adjust the tensioning of the top and bottom skins respectively.
In a known construction of musical drum as described in U.S. Pat. No. 1,090,426, a tensioning adjustment system is described in which the tension of both the top and bottom skins can be adjusted from the same face of the drum. However this system is suitable only for drums of the type in which the fittings by which pressure is applied to the skin are secured to the drum shell itself. The system described therefore suffers from the disadvantage of deterioration in sound quality and mechanical weakening as discussed above and therefore does not meet current commercial requirements.
In addition, it is a further disadvantage of the drum described in U.S. Pat. No. 1,090,426, that when a skin has to be replaced, the fixing bolts have to be retensioned and the drum has to be retuned.